Evaluation Of Associative Effects Of Corn Silage And Sweet Potato Vines And Their Effects On Fattening And Meat Quality Of Dairy Bulls

Experiment 1:assessment of associative effects of whole corn silage and sweet potato vines by gas production in vitro.On the basis of the theory of multiple factors associative effects index?MFAEI?,the associative effects between the whole corn silage?WCS?and sweet potato vines?SPV?,corn stalk silage?CSS?and SPV were investigated by gas production method in vitro to screen out their appropriate combination ratio.Seven groups of combinations of WCS and SPV,CSS and SPV?100:0,90:10,80:20,70:30,60:40,50:50,0:100?were selected for 48hours fermentation in vitro.Then the fermentation indicators,gas production yield and the associative effects index were calculated and analyzed.The results showed as follows:1)The combination of WCS and SPV:the dry matter disappearance rate,microbial protein,volatile fatty acid and gas production were significantly or very significantly different in all proportions?P<0.05 or P<0.01?.In addition to pH and NH₃-N,the fermentation indicators of each group decreased first and then increased with the increase of SPV addition.Comprehensive analysis showed that the optimum combination ratio of WCS to SPV was 50:50,and the MFAEI was 0.19;2)The combination of CSS and SPV,the dry matter disappearance rate,microbial protein,volatile fatty acid and gas production were significantly or very significantly different in all proportions?P<0.05 or P<0.01?.In addition to pH,the fermentation indicators of each group were increased with the increase of the amount of SPV addition.The results showed that the optimum combination ratio of corn straw silage to sweet potato vines was 50:50.Experiment 2:Effects of SPV replacing 50%WCS on fattening performance,slaughter traits and meat quality of dairy bullsThis experiment was conducted to explore the effects of sweet potato vines?SPV?replacing whole corn silage?WCS?on fattening performance,nutrient apparent digestibility,blood index,slaughter traits,meat quality,fatty acids in meat and economic benefits of dairy bulls.Thirty dairy bulls with an average weight of about 503.19±11.83kg were selected and divided into two groups with 15 bulls in each group.The group I was fed whole-plant corn silage only,while group II was 50%SPV+50%WCS,the other feeding conditions of the two groups were consistent.The results showed:1)There was no significant difference in daily gain and feed-weight ratio between the two groups?P>0.05?.Dry matter intake in group I was significantly higher than that in group II?P<0.05?;2)The apparent digestibility of ADF in group II was significantly higher than that in group I?P<0.05?,but there was no significant difference in other indicators?P>0.05?;3)Blood index between groups was not significant?P>0.05?;4)Although there was no significant difference in slaughter traits and meat quality between the two groups?P>0.05?,water loss rate and cooking loss in group I were 9.87%and 2.11%higher than those in group II,respectively;5)The level of C18:1n9c in group I was significantly higher than that in group II?P<0.05?,MUFA was 6.18 percentage points higher than that in group II?P>0.05?,and the level of C18:2n6c was significantly increased in group II?P<0.01?;6)The daily income per cow of group II was 1.57 yuan higher than that of group I.In conclusion,it is feasible to replace 50%WCS with SPV in fattening dairy bulls.